Compound master cylinder



May 23, 1950 E. KNAUSS 2,508,403

COMPOUND MASTER CYLINDER Filed Dec. 1l, 1945 a r 2%" l /6 l l /V W W, 46 /4 50 INVENTOR. 1/4 4Z EDWARD KHAUSS BY @Mv M? Patented May 23,

aa mountain-bigot ofllthenpresenltlnvention is to provide a devcefwhichwill Bc'kpressurefihcrease-fonthe @om fr defun@ b fessure. C.pm-mary pisfb'n.

The body I8 has a fluid reservoir 28 preferably formed integral therewith and provided with a vented and screw threaded plug or cap 22 which maintains the reservoir at atmospheric pressure. A port 24 connects reservoir 28 with the primary cylinder I2 when forwardly of piston 52 in the inoperative relationship and is closed on the pressure stroke by theinner flange 62 of the piston. The reservoir 28 may be provided with a removable cover plate II fastened to the body Iv cured by screws I5.

The device is provided with a novel'pressure d which for convenience may be termed the high pressure cylinder and within it are the high pressure piston 38 and the piston cap 21. The upper portion of piston 38 is crowned to leaveopenings 40 permitting communication with cylinder I2 via channel 29 with the piston raised, and the top of open-ended cylinder isfaced to form a seat 28 for the disc 3| of overlying centrally apertured diaphragm 30. Surrounding the cylinder 26 and the valve seat 28, the casing I0 is bored and faced to mount the diaphragm 30 which is secured in place by a cap 32 attached by any suit-V able means as screws 33. Within the cap 32 is a control spring 36 which bears against the diaphragm backing plate and a screwv plug or Vadjusting nut 34 by which the compression of the control spring may be adjusted. The adjustment of thek plug 34 regulates the pressure with which the diaphragm 3,0 is held upon the valve seat 28 and so controls the pressure which the piston 26 must exert to unseat the diaphragm. Adjustable communication between the reservoir 28 and the primary cylinder I2v via channel 28,

opening 48, and the aperture in diaphragm 3D, is

thus established.

VAs vstated before, a secondary cylinder I4, is located concentrically with respect to the primary cylinder I2.Y A centrally apertured piston 42, having a piston cup 43 and a central seal 44 around said central aperture, is reciprocally mounted within the` ksecondary cylinder I4, and normally urged toward the open end of said cylinder and toward a split ring'stop 48 by a spring 46. The other end of said Aspring impinges against a double check valve 5.0 which normally seats against the open end of reduced chamber I6 in the restricted end of the secondary cylinder I4.

This check valve 58 is constructedV and arranged to restrict passage of fluid under pressure from the secondary cylinder I4, to a braking mechanism, hereinafter described, in order to prevent sudden slamming or locking of the brakes.

.Being physically displaceable against the action "voir 28 of the bodyl. l

Adjacent to the inner ange 62 of the pistonZ-,

4 when in its outer or inactive position is a port 64 also communicating with the reservoir` 20 and normally closed on the forward or pressure stroke by a flanged cup washer 66 and the said piston flange 62. It is through this port 64 that fluid is supplied to replenish the primary cylinder after pressure is released. The inner end of the primary piston 52 is also provided with a preferably cylindrical extension or plunger 68, the end of which is, with piston 52 in its inoperative position, in spaced relation to the secondary piston 42.

Upon forward movement of the piston, however, plunger 88 is adapted to contact and actuate the secondary piston 42. The spacing of plunger 68 from the secondary piston 42 is provided to compensate for average brake adjustments and brake-shoe wear, and permits the initial movement of piston 52 to iill the system with fluid and to start the initial application of the brakes.

A push rod 'I8 has a free hemispherical end seated within the socket 54 of the primary piston 52 and the other end, for example, may be pivotally connected to a brake pedal 'I2 plvotally mounted upon a support 'l5 Yand connected by a retractile spring 'I6 to a xed support 18. The linkage may be accomplished in any conventional or suitable manner.

The braking mechanism comprises fluid pressure delivery conduits or lines 80 connecting the ports I8 of the reduced chamber I6 to fluid pressure actuated brake vcylinders 82 having the usual pistons (not shown) connected to brake shoes 84 within the usual brake drums 86, said shoes 84 being normally held in retracted or inoperative positions by the usual springs 88.

It should be understood that the primary and secondary cylinders I2 and I4, respectively, conduits and brake cylinders 82 are charged with a suitable uid (not shown) which is subject to pressure or pedal force, while the reservoir 20 and annular space between the anges 60 and 62,

of the primary piston 52 are charged with iiuid (not shown) under substantially atmospheric pressure, the purpose and effectiveness of which will presently appear.

The device illustrating the invention operates as follows: Assuming the normal rest or inoperative position, shown in Figure 2, with the primary and secondary cylinders charged with fluid as well as a reserve in the reservoir 20, initial movement of the pedal 12, through push rod 1I) and primary piston 52, will initiate the pressure stroke. Immediately by virtue of the movement of piston 52 a, comparatively large volume of fluid (not shown) is displaced from the primary cylinder I2, through the centrally apertured secondary piston 42, the secondary cylinder I4 and the double check valve 50, into reduced chamber I6, out ports I8 and into conduits 88 to the brake cylinders 82 at a. low pressure i. e. a pressure less than the control pressure of the system as set by the adjusted spring 36) to take up slack, charge the pistons 82 and effect sufs fcient pressureto produce a slight drag of the shoes 84 upon the drums 86 and initiate the braking. The iirst slight pedal pressure moves piston ,52 sufficiently to cause the cup 66 of piston flange 62 to seal oi and close port 64. so

, that fluid in the primary ncylinder I2 will be cut oli from reservoir 28 and `so subjected to the initial low pressure exerted by the operator upon the pedal. A minimum movement of the pedal l2, therefore, will instantly operate to charge the system preparatory to applying a braking load. All of this is accomplished by or before of ,theseeendary pisttnw.. lie 9195er; 0.1i the 110W 9i llqiiid from,- the. primary cylinder and into the Secondary risien Ye tneslieiitfeieteneeie enlise the plnneeriifielenease nistea'tathere: bnclesineieriseaine efr. the. centrar-aperture th reci end stepmne'iiieaflew @friert Pressure ai Lthesysteniiliurthe nressureiunonf 10 e moy/,ement Qgtnapeqalj move s aid-nist en eiltien amnehsm .11er increase-gefafereeliaiile 4, A SariSien? netleih malintesi@ e. .epeeted is required, to' is efe tnanetne diameter'eime inereeeeitnerbra A primerrnistene?. i .iaebrieustbat-thevolume ci Enid dispiacedamil,badecreased Istit-thei fluid press e willi be areatly iinereaeedl-and Said fluid will. ioreedaiihreilshithe check .yelre i511.. ecris it.. enndnits; .&0;and. .i fie-tire drumieylinders 8 3 sti` n increased @presen te produce a braking effectief theshees n.; rams 86.. theioreeeina it.. ,be ebserve rtliat aitenalarse. rolumeeniiuid .has beeneispIaced i nnder-.eomparatirelr low nressnre by. an initial, within the-Seconda minimum; mal/.ement or A w the pedal `'HMA iu-rtlfler 5. dirgli/ill mOVe the movement thereon isidirectedtc. themeving of a small volume of'fluid under an increased presbeep .d eieaii; QFQCK-YYP iisife t n sure. ily hiermit;c ae; uf1 r e .striet e flew ef. .-iiuisi With the alosiilg-of-thaaperture of the sec-A e -drue1 ey1.i nders,2, thereby instantly en dampisten fi? 12x-the inneren@ offline-plunger f Y, K8, theps's'ure which i'sbeingbbdtfup by the further moyemeiit oi .piston sg wii1f be trans'- mitted to'th'e`diaphragmi30"through channel 29 andfvwhn sufficiently greatfinl combination-with the' pressure acting lon. thehigh pressure piston y, 3`8',"wil1 caus'elitfto raise fromritsseat 2`8`,ia`gainst the force'o'f .thespringi36 underlthe regulating ,C lprlsl immediately tg plagiat. Thispermitsiherpassage or release of reset t i 1e system., pressure ei theleenftheelarge'fexcesswolumeof'fluidunderllowlpedal iirOllSprirlg ,35 Qrriiiapiilagm 3 0 @Xd 'presr pressure'from. .theprimaryacylinder I2', through Sure ,orithelpedalnihel C Qritrlyalvevassembly sid pertufed,wdiaphragmnfand,aperturedplug 4o will immediate1y be .returned and. reset t0 the 3dS-.and .into the..reservoirr=2l) which is always'at position shown in Figure 2. After pressure is atmospheric .,pressure V.At .the same time` the removed from the pedal A12, the springs 46 and pedalpressure.requiredtotmove'the liquid in the 58.. will. quickly` return, theirfreSDQCtiVe DiSiQD! secondarycylinder .isreduced'without dir'ninishagainstitheir respective stops,f arid the Springs ingthervolume displaced. a '4"5 88, will retractthe shoes 84 from the drums rea Accordingly-gastthegfluidgp ssure between the leasing :the brakes; ,i A SeCOriSiarY piston`42` and brakj' cylindersz, DIQ- .:..A,device:,for centrally `controlling the ow of duedljby fgurther mov `VrMeint ointhe `pedal 12, yfiuidto'the individualbrake devicesis .generally builds' u'pl it Will" b: exerted against and Will A?, referred to and' known as a compound master actuate the cap 21 and high pressure piston 38 5G cylinder; within the high pressure cylinder 26 of the sec- I claim; ondary cylinder I4. The combined pressures eX- 1. In combination, a compound master cylinder erted 0n the diaphragm 30 Will raiSe it from its unit for liquid pressure systems comprising a fluid Seat and permit a iOW. 0111i' When they OVEI- reservoir, a primary cylinder communicating come the resistance 0f the ConirOl Spring 36. 55 therewith and containing a piston for exerting Which iS usually Set at 50 P S- I- pressure, a secondary cylinder communicating It will be observed that as the feet Pedal 12 with said primary cylinder only in oir and initial is being depressed the Scondafy DlSOD 42 iS application of pressure, a release valve for fluid moved forward. This builds up the line presfrom said primary cylinder including a diasure to the brakes and at the same time the o0 phragm formed with a pol-1; and positioned bellid pressure in front of the primary piStOrl 52 tween said primary cylinder and said reservoir, builds up t0 the COIltI'Ol Setting 0f the ('201'111101 and a high pressure Cylinder cpan to said sec.. spring 36 so that the required foot pedal force ondary cylinder and a piston having a castellated uniformly increases until the fluid pressure 1S end adapted to contact said diaphragm around released in front 0f the primary DiSOIl 52. It iS 65 said port, characterized in that said diaphragm true, therefore, that aS the fluid pressure under is movable under the pressure exerted therereleased diaphragm 30 from cylinder I2 is reduced it peragainst by said high pressure piston and by fluid mits spring 36 to exert more and more force in said primary cylinder.

against piston 38. thereby requiring a substan- 2. A compound master cylinder unit for liquidI tially increasing amount of secondary piston 70 pressure systems comprising a uid reservoir, a pressure to overcome the effective spring load primary cylinder communicating therewith, a Further increase in the line pressure beyond this primary piston in said cylinder for exertingpoint causes the foot pedal force to build up pressures, a secondary high pressure cylinder-- slightly faster for each 100 P. S. I. axially aligned with said primary cylinder adapt-.

The system is controlled by the valve assem- 75 ed to connect to a brake motor, a. secondary pis-i.

Y,alsosnios *ton in said secondary cylinder, a high pressure Pcylinder open into said secondary cylinder for- `wardly of said secondary piston, a high pressure piston in said high pressure cylinder, a centrally .ported diaphragm in the wall of said primary cylinder adapted to make sealing contact with 'the end of said high pressure cylinder in its closed position, said high pressure piston being movable to contact said diaphragm to move it from said high pressure cylinder with the aid ot the pressure in said primary cylinder acting thereonI to enable fluid under pressure to escape from said primary cylinder, and tension means to control the force required to move said diaphragm to open position.

3. A compound master cylinder unit for liquid pressure systems comprising a fluid reservoir, a primary cylinder communicating therewith, a primary piston in said cylinder for exerting pressures, a secondary high pressure cylinder axially aligned with said primary cylinder adapted to connect to a brake motor, a secondary piston in said secondary cylinder, a high pressure cylinder open into said secondary cylinder forwardly of said secondary piston, a high pressure piston in said high pressure cylinder, a centrally ported exible diaphragm closing an opening in the wall of said primary cylinder and positioned as to be contacted, when in its closed position, by the open end of said high pressure cylinder to close its central port from said'primary cylinder, said diaphragm being actedupon by iiuid under pressure in said primary cylinder on its 'surface at the sides of said high pressure cylinder, the high pressure piston in said high pressure cylinder being movable into contact with said diaphragm under the pressure of fluid in said secondary high pressure cylinder to move said diaphragm to break its seal with said high pressure cylinder to enable iiuid from said primary cylinder to pass through its central port and into said reservoir.

4. In a compound master cylinder unit for liquid pressure systems of the type in which a. low pressure cylinder-piston unit and a secondary high pressure cylinder-piston unlit sequentially provide fluid under pressure to a receiving conduit; a fiuid reservoir; a low pressure cylinder connected by openings at longitudinally spaced points to said reservoir, a spring-urged valve closing one of said openings, said valve including fig a centrally ported flexible diaphragm exposed to fluid pressure within said low pressure cylinder exteriorly of said central portan'd a seat, said port being adapted tobe closed by said seat, a piston slidable in said low pressure cylinder adapted to close one of said openings in its advance in said cylinder; a secondary high pressure cylinder axially aligned with said low pressure cylinder and formed in its wall with a laterally extended high press-ure cylinder positioned adjacent said valve and serving as 'said seat therefor, a piston in said laterally extended high pressure cylinder adapted in itsadvanced position to contact said valve and liftit from its seat to open said part, and a ported piston in said sec..v ondary high pressure cylinder positioned as to be contacted by means movable with the piston in said low pressure cylinder after a predetermined independent movement thereof to close the port therein, the advance of said ported piston forcing iiuid at relatively high pressure from said secondary high pressure cylinder into a conduit and serving to advance said piston in said laterally extended cylinder to exert a valve-lifting force in the same direction as said pressure on said diaphragm to open said valve.

EDWARD KNAUSS.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 486,501 Phillippi Nov. 22, 1892 1,608,618 Richards Nov. 30, 1926 1,709,150 Pieper Apr. 16, 1929 1,919,465 Furgason July 25, 1933 1,958,722 Sinclair May 15, 1934 2,036,342 Loweke Apr. 7, 1936 2,184,501 Loweke Dec. 26, 1939 2,190,238 Lepersonne Feb. 13, 1940 2,196,190 Bowen Apr. 9, 1940 2,215,602 Baade Sept. 24, 1940 2,298,848 Swift Oct. 13, 1942 2,317,604 Hamilton Apr. 27 1943 FOREIGN PATENTS Number Country Date 515,709 Great Britain Dec. 12, 1939 Y Certificate of Correction Patent No. 2,508,403' y May 23, 1950 l EDWARD KNAUSS numbered-fpatent requiring correction as followsg ,Y y v v Column 8, lnf1l5fffortphe Word part readport;4 andvthat the said Letters Patent should be read as corrected above, so that the same may conform to the 'eooi'df the oase inV the Patent Oilce. Signed and sealed this 10th day of Ootober, A. D. 1950.

It is heli-roby o'e-tied that error appears-,inthe printed specoatio of thossboy `:7**"THOMAS "F, PHY,

Assistant Commissioner of Patents. 

